From: Anatoly Burakov <anatoly.burakov@intel.com>
To: dev@dpdk.org
Cc: bruce.richardson@intel.com
Subject: [dpdk-dev] [PATCH v2 2/2] mem: unmap unneeded space
Date: Mon, 30 Apr 2018 12:21:43 +0100 [thread overview]
Message-ID: <73e35ca9ce462ab097c6ca8e7cbfdd5b8bc06c1d.1525086045.git.anatoly.burakov@intel.com> (raw)
In-Reply-To: <fb6d9b6f3bbead5f9ab3e9906814d35431b9edf5.1525086045.git.anatoly.burakov@intel.com>
In-Reply-To: <be863f870fc02ea6464d15c87fa43e9d274f3240.1524155435.git.anatoly.burakov@intel.com>
When we ask to reserve virtual areas, we usually include
alignment in the mapping size, and that memory ends up
being wasted. Wasting a gigabyte of VA space while trying to
reserve one gigabyte is pretty expensive on 32-bit, so after
we're done mapping, unmap unneeded space.
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
Notes:
v2:
- Split fix for size_t overflow into separate patch
- Improve readability of unmapping code
- Added comment explaining why unmapping is done
lib/librte_eal/common/eal_common_memory.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index 0ac7b33..60aed4a 100644
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -121,8 +121,32 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
RTE_LOG(DEBUG, EAL, "Virtual area found at %p (size = 0x%zx)\n",
aligned_addr, *size);
- if (unmap)
+ if (unmap) {
munmap(mapped_addr, map_sz);
+ } else if (!no_align) {
+ void *map_end, *aligned_end;
+ size_t before_len, after_len;
+
+ /* when we reserve space with alignment, we add alignment to
+ * mapping size. On 32-bit, if 1GB alignment was requested, this
+ * would waste 1GB of address space, which is a luxury we cannot
+ * afford. so, if alignment was performed, check if any unneeded
+ * address space can be unmapped back.
+ */
+
+ map_end = RTE_PTR_ADD(mapped_addr, (size_t)map_sz);
+ aligned_end = RTE_PTR_ADD(aligned_addr, *size);
+
+ /* unmap space before aligned mmap address */
+ before_len = RTE_PTR_DIFF(aligned_addr, mapped_addr);
+ if (before_len > 0)
+ munmap(mapped_addr, before_len);
+
+ /* unmap space after aligned end mmap address */
+ after_len = RTE_PTR_DIFF(map_end, aligned_end);
+ if (after_len > 0)
+ munmap(aligned_end, after_len);
+ }
baseaddr_offset += *size;
--
2.7.4
next prev parent reply other threads:[~2018-04-30 11:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-19 16:35 [dpdk-dev] [PATCH] " Anatoly Burakov
2018-04-27 16:32 ` Bruce Richardson
2018-04-27 16:38 ` Bruce Richardson
2018-04-30 11:21 ` [dpdk-dev] [PATCH v2 1/2] mem: check if allocation size is too big Anatoly Burakov
2018-04-30 12:49 ` Bruce Richardson
2018-04-30 11:21 ` Anatoly Burakov [this message]
2018-04-30 12:50 ` [dpdk-dev] [PATCH v2 2/2] mem: unmap unneeded space Bruce Richardson
2018-05-02 21:00 ` Thomas Monjalon
2018-05-08 20:20 ` Thomas Monjalon
2018-05-13 23:33 ` Thomas Monjalon
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